Moving from one end of the stage to the other, sweat streaming from his face, the singer went on to describe, with unprintable detail, the physical effect his songs were having on him.

He strung together snippets of 10 or 12 of them -- “Snake,” “I’m a Flirt,” the immortal “Bump N’ Grind” -- and seemed openly amazed by how powerful even the oldest remain.

As he warned, Kelly was getting deep into his worldview here. Really, though, he spoke his mind for the duration of this nearly two-hour show; at no point did he smooth out his well documented kinks.

The subject throughout, of course, was sex, albeit in an astonishing number of permutations, from the metaphysical (“Number One”) to the automotive (“You Remind Me of Something,” in which the something is Kelly’s Jeep.)

Friday’s performance, the first of two at Nokia over the weekend, took place several weeks into the Single Ladies tour, undertaken ostensibly in support of this summer’s “Write Me Back” album.

Lovingly produced in the old-school style of Barry White and Teddy Pendergrass, the record is a sequel of sorts to 2010’s similarly retro-minded “Love Letter.” It contains a sumptuous piece of orchestral disco called “Feelin’ Single,” which presumably inspired Kelly’s most prominent costume piece on Friday: a white-leather jacket with the word “single” in light-up letters running down the left sleeve.

Yet beyond his wardrobe Kelly didn’t adhere all that closely to “Write Me Back.” He even skipped “Feelin’ Single.” In its substance the Single Ladies tour delivers the same experience as the Love Letter tour and the Ladies Make Some Noise! tour, both of which Kelly brought to Nokia in recent years.

That amounted to a kind of running monologue usually set to music, but not always: During one lengthy stretch he joined verses and choruses from a handful of old songs (including “12 Play” and “Real Talk”) without accompaniment, pushing his voice into a scratchiness he typically avoids.

One of his finest set pieces came before “Slow Wind” ("wind" rhymes with “find”), when he leaned down to listen to a fan’s whispered description of what she and Kelly might accomplish together. Nodding eagerly, he suddenly recoiled in mock-revulsion, exclaiming, “I’m R. Kelly, and I’ve never heard of that.”

Occasionally his expansive vision took in what appeared to be a contradiction, as when he followed a disturbing sequence in which he locked a woman inside a cage with the new album’s “Green Light,” a tender slow jam about respectfully waiting for permission to proceed.

There were dull patches too, including an amazingly lazy bit he referred to as “Kells Karaoke.” Imagine the singer enjoying a drink at one of the concert’s two onstage cocktail bars while the audience sings some of his hits for him.

But perhaps Kelly was summoning the energy required for the final push Friday, in which he performed complete versions of three of his most thrilling songs: “I Believe I Can Fly,” reclaimed somehow from the depths of mid-’90s “Space Jam” schmaltz; the Percy Sledge-style ballad “When a Woman Loves”; and “Step in the Name of Love,” Kelly’s effervescent ode to the dance form known as stepping in his hometown of Chicago.

Several dozen women joined the star onstage for that final number, moving around him in a reasonable simulacrum of a crowded Windy City nightclub. As always, Kelly was steering the narrative. And the ladies -- single or otherwise -- were happy to be part of the story line.